Neon tube



Oct. 23, 1928. v 1,689,146

I R. R. MACHLETT NEON TUBE Filed Oct. 20, 1926 INVENTOR ATTORNEY Patented a. 23, 1928.

UNITED STATES PATENT: OFFICE- RAYMOND ROBERT macn'mrsr, or-Nnw YORK, N. 1., ASSIGNOB 'ro RAINBOW LIGHT,

. INC., A CORPORATION or NEW YORK.

NEW minim Application filed October 20, 1926. Serial No. 142,839.

My invention relates to various-new and useful improvements in luminous tubes, particularly those in which a conducting atmosphere of neon is used. I prefer to make I) use of neon owing to its brilliant. and attractive color when rendered luminous by a high tension discharge, but the invention can also be utilized with other monatonic inert gases of the so-called noble group, including argon,

w helium, krypton'and xenon, all of which have their characteristic spectra. These latter gases however do not possess the extremely favorable characteristics of neo In the manufacture of neon bes, prior to my invention, it was considere necessary to make use of relatively large electrodes .of.the order of fifteen or more square decimeters per ampere of current, in order to minimize the henoinenon of electrical evaporation observed by Sir Wm. Crookes and referred to forexample by E. G. Baly The Spectra of Neon, Krypton and Xenon Philosophical Transactions, Royal, Society, 1903, A. 202, page 185. As B'aly .points out in this article,

: neon is absorbed by the electrode metal de-' posited upon the wallsof the tubes, thus depleting the atmosphere and shortening the life of the ti1be.' c, 7

Even when neon tubes are made with electrodes having an area of fifteen or more square decimeters per ampere of; current and the negative glow does not cover the entire electrode. surface, there is a ver substantial energyloss due to the sharp fal of'potenti'al between'the electrodes. and the luminous column.

With my improved neon tube, as will'be hereinafter described, I am enabled to make use of electrodes of as small an area, as .9

40 square decimeters per ampereand to operate the tube with such electrodes in an entirely .eflicient and useful way, and without undue heating or sputtering of the electrodes. At

the same time, I improved the efiiciency, be-

, 1 :1 cause with the tube of my invention the capacity reactance is materially reduced, while the ohmic resistance is increased.

In explanation of the statement just-made,

I point out that when voltage is applied to a '50 neon or other gas discharge tube, this voltage is utilized to overcome the usual components of impedance offered by a circuit to the flow l 5 of alternating current. By actual test it has been found that the totalvoltage drop is due I to two components of impedance-one due to .provided with interior electrodes and if a capacity which results mainly from the electrical conditions at the electrodes where a very large percentage of positive ions are accumulated as'each electrode functions as a cathode; and the other due to pure ohmic resistance in the luminous column itself where the negative and positive ions exist in approximately equal proportions.- The luminous efiect is aifunction of the ohmic resistance and any increase in this impedance factor results in greater luminous efficiency.

- Specifically I have discovered that if a luminous tubefilled with neon or other .monatomic gas under reduced pressure, is

mirror of an electro-positive alkali metal, such asymetallic'caesium is deposited upon the tube walls somewhat 'in advance ofeach electrode, very remarkable andunexpected results are secured. With such a tube, the electrodes do not heat in operation even when of very smallarea and therefore'the vaporization effect is very substantially reduced. Furthermore the distribution of energy is so altered as to result-in an increase of ohmic resistance in the gaseous column and thus a more effective application of energy for illuminating purposes. Such an increase of efliciency has actually been measured in terms of wattage and may amount to as much as 20% as compared to that of a standard neon tube without caesium and having electrodes of large area.

In order that the invention may be better understood, attention is directed to the accompanying drawing in which a tube is shown embodying my present invention and in connection wit which I will describe the use of metallic caesium as the electro-positive alkali metal. e 9 The main body of the tube 1, is made of glass of suitable dimensions and is generally bent into the form of a symbol or letter for advertising purposes. Owin to the fact that the improved tube lends itsel solfavorably to use with currents of great magnitude, it may be, and hasbeen efiectively utilized as a bea con light for aerial navigation; For such use, tubes of from three to five meters in length have been operated with currents of 5 and more amperes through the tube, thus giving a concentrated source of illumination of intense brilliancy. The ends of the tube are enlarged at'2, as shown, and within each enlargement is a stem,,3, formed integral no therewith, upon which stem is mounted the electrode; 4, generally a. thin copper' shell. Current is conveyed to each electrode by the usual conductor 5. The maximum area of the electrode is practically immaterial, but in practice I have made t em with an area of only .9 square decimeters per ampere or even less. Their size depends largely upon convenience and ease of construction from a mechanical int of view. The enlarged ends of the tu e as shown, are preferably conical or pear shaped, providing a chamber of substantial size surrounding each electrode. During the final stages of exhaustion of the tube and just prior to the admission of the.

neon gas in the tube, a mirror of pure metallic caesium 6 is distilled into the chamber surrounding the electrode and manipulated by heatin so as to deposit it in the general position il ustrated. I

The formation of the tube may be carried out in any suitable way, but I prefer to make use of t e purifying method disclosed in my -patent ranted February 22, 1927, No. 1,618,767, w erein the tube is subjected to a baking operation at a high temperature during its exhaustion, followed by a special purification process involving the use of a vapor of an alkali metal. In my said application I suggest particularly the use of metallic po tassium as the alkali metal, the vapor of which is to be used in effecting the final stages of purification of the tube, but I find that caesium can also be employed for the purpose and therefore I utilize the va or of caesium in the same wa as the vapor o metallic potassium,

. as descri d in said application. The caesium is thus used as a matter of convenience, since it is at hand.

After the tube has been thus thoroughly purified by the vapors of metallic caesium, the temperature of the tube is reduced as disclosed in said application, after which, when the tube has cooled, the caesium mirror is formed adjacent to the electrodes, as I have already described. Such a process of purification is e'xtremely effective, and when the neon is introduced. at a pressure of about 8 millimeters of mercury, the most desirable results will be secured.

As I have indicated, the presence of the 1 caesium'mirror in the neighborhood of the electrodes therein having an area less than one square decimeter per ampere and a deposited mirror-"g of anelectro-positive metal on the walls of the tube adjacent to the cathode, as

set forth. 2. A luminous tube containing a conduct: mg atmosphere of a monatomic inert gas,

electrodes therein having an area less than one square decimeter per ampere and a deposited mirror of metallic caesium onthewalls of the tube adjacentto the cathode, assetfforth,

3. A luminous tube containing an 'atmos phere of neongag-electrodes therein having an area oflessthan one square decimeter per ampere and a'deposited mirror of an electropositive metal on the walls of the tube adjacent to the cathode, as set forth.

4. A luminous tube containing an atmosphere of neon gas, electrodes the'reinhaving an area of less than one square decimeter pen ampere and a deposited mirror of metallic caesium on the walls of the tube adjacent to.

the cathode as set forth.

RAYMND ROBERT MACHLETT. 

